1. Field of the Invention
The present invention relates to pressure measurement devices, and in particular, to pressure measurement devices which measure and selectively process relative pressure differentials corresponding to opposing pressure thresholds.
2. Description of the Related Art
As the sophistication and costs of solid state pressure measurement devices, such as altimeters, have increased and decreased, respectively, their uses have become varied and widespread. With respect to sports-related activities, various types of accumulating altimeters, in particular, have become popular. For example, U.S. Pat. No. 5,058,427, which is commonly assigned to the assignee of the present invention and the disclosure of which is hereby incorporated by reference, discloses an accumulating altimeter having ascent and descent accumulation thresholds particularly suitable for bicyclists. The altimeter disclosed therein has selective ascent and descent accumulation thresholds which allow the altimeter to initially ignore altitude gains or losses below predetermined amounts, while accounting for altitude gains and losses exceeding such predetermined amounts.
As a further example, U.S. Pat. No. 4,694,694 discloses an altimeter which accumulates and displays altitude gains or losses over selected intervals. As disclosed therein, this type of altimeter can be useful for snow skiers who wish to accumulate total altitude changes during a day of skiing.
While altimeters, and particularly accumulating altimeters, can be useful for many sports-related activities, some activities may require some processed form of altitude information other than a mere accumulation. For example, it would be desireable in some activities to determine not only the present altitude or the cumulative altitude changes, but to also determine how many opposing altitude transitions of a selected magnitude have been encountered.